The neuronal systemThe hormonal system

What conditions must be kept constant inside the body?

What processes must occur in order to maintain a constant internal environment?

Any change in the internal environment must be detected.The changes must be signalled to other cells.There must be a response that reverses the change.

9

What is the standard pathway used to produce a suitable response to a stimulus?

stimulus -> receptor -> cell signalling -> effector -> response

10

What structures are required for the standard pathway used to produce a suitable response to a stimulus?

Sensory receptors, such as temperature receptors or glucose concentration receptors.A communication system, such as the nervous system or hormonal system.Effector cells, such as liver cells or muscle cell.

11

What do sensory receptors do in the process of negative feedback?

These receptors are internal and monitor conditions inside the body.If they detect a change they will be stimulated to send a message.

12

What does a communication system do in the process of negative feedback?

It acts by signalling between cells.It is used to transmit a message from the receptor cells to the effector cells,The message may pr may not pass through a coordination centre such as the brain.

13

What do effector cells do in the process of negative feedback?

They bring about a response that reverses the change detected by the receptor cells.

14

What is an example of positive feedback that has a negative effect on the body?

Below a certain core body temperature the enzymes become less active.If they are less active the exergonic reactions that release heat are slower and release less heat.This allows the body to cool further and slows down the enzyme-controlled reactions even more, so that the body temperature spirals downwards.

15

What is an example of when positive feedback is beneficial?

At the end of pregnancy to bring about dilation of the cervix.As the cervix begins to stretch the change is signalled to the anterior pituitary gland, stimulating it to secrete oxytocin.Oxytocin increases the uterine contractions, which stretch the cervix more, which cause secretion of more oxytocin.

16

How do ectotherms keep warm and why?

External sources of heat.This is because they are not able to increase respiration rates to generate heat internally.

17

What are the advantages of being an ectotherm?

Use less of their food in respiration.Need to find less food and may be able to survive long periods without eating.A greater proportion of the energy obtained from food can be used for growth.

18

What are the disadvantages of being an ectotherm?

Less active in cooler temperatures, and may need to warm up in the morning before they can be active. This puts them at greater risk of predation.May not be capable of activity during the winter as they never warm up sufficiently. This means they must have sufficient stores of energy to survive over winter without eating.

19

How do ectotherms regulate their body temperature?

When one is cold it will change its behaviour or physiology to increase absorption of heat from the environment.When one is hot is will change its behaviour or physiology to decrease absorption of heat and increase loss of heat to its environment.

20

What adaptions do snakes have and how does it regulate temperature?

Expose body to sun - Enables more heat to be absorbed

21

What adaptions do locusts have and how do it help regulate temperature?

Orientate body to sun - Exposes larger surface area for most heat absorptionOrientate body away from sun - Exposes lower surface area so that less heat is absorbed.Increase breathing movements - Evaporates more water.

22

What adaptions to lizards have and how does it help to regulate temperature?

Hide in burrow - Reduces heat absorption by keeping out of the sun.Horned lizards alter body shape - Exposes more or less surface area to sun.

23

How do endotherms maintain body temperature?

Internal sources of heat.Behavioural and physiological mechanisms.

24

What are the advantages of being a endotherm?

A fairly constant body temperature whatever the temperature is externally.Activity possible when external temperature are cool.Ability to inhabit colder parts of the planet.

25

What are the disadvantages of being an endotherm?

A significant part of the energy intake used to maintain body temperature in the cold.More food required.Less of the energy from food is used for growth, or more food is needed in order to grow.

26

What are the main physiological components used to maintain body temperature in endotherms?

Sweat glands in skinLungs, mouth and noseHairs on skinArterioles leading to capillaries in skin.Liver cellsSkeletal muscles

27

How do sweat glands help to maintain body temperature?

If temperature is too high they secrete more sweat onto skin; water in sweat evaporates, using heat from blood to supply latent heat of vaporisation.If temperature too low less sweat is secreted; less evaporation of water, so less loss of latent heat.

28

How do the lungs, mouth and nose help to maintain body temperature?

If too high panting increases evaporation of water from lungs, tongue and other moist surfaces, using latent heat.If too low animal does not pant, so less water evaporates.

29

How do the hairs on skin help to maintain body temperature?

If too high hairs lie flat, providing little insulation, and thus more heat can be lost by convection and radiation. If too low hairs are raised to trap a layer of insulating air, reducing the loss of heat from the skin.

30

How do arterioles leading to capillaries in skin help to maintain body temperature?

If too high vasodilation allows more blood into capillaries near the skin surface; more heat can be radiated from the skin.If too high vasoconstriction reduces the flow of blood through capillaries near the the skin surface; less heat is radiated.

31

How do liver cells help to maintain body temperature?

If too high rate of metabolism is reduced, less heat is generated from exergonic reactions.If too low rate of metabolism is increased, therefore respiration generates more heat, which is transferred to the blood.